Bonded substrate and its manufacturing method

Abstract

In a bonded substrate according to an embodiment, Euler angles (φ1, θ1, ψ1) of a first quartz-crystal substrate satisfy 0°≤φ1≤2°, 123°≤θ1≤128°, and 31°≤ψ1≤44°, Euler angles (φ2, θ2, ψ2) of a second quartz-crystal substrate bonded over the first quartz-crystal substrate satisfy 83°≤φ2≤95°, 82°≤θ2≤95°, and 159°≤ψ2≤161°, and a thickness of the second quartz-crystal substrate is 0.17 to 0.19 times a wavelength of a surface acoustic wave.

What is claimed is: 
     
         1 . A bonded substrate, comprising:
 φ1 a first quartz-crystal substrate; and   φ1 a second quartz-crystal substrate bonded over the first quartz-crystal substrate, wherein   Euler angles (φ1, θ1, ψ1) of the first quartz-crystal substrate satisfy 0°≤φ1≤2°, 123°≤θ1≤128°, and 31°≤ψ1≤44°,   Euler angles (φ2, θ2, ψ2) of the second quartz-crystal substrate satisfy 83°≤φ2≤95°, 82°≤θ2≤95°, and 159°≤ψ2≤161°, and   a thickness of the second quartz-crystal substrate is 0.17 to 0.19 times a wavelength of a longitudinal leaky surface acoustic wave which propagates across a surface of the second quartz-crystal substrate.   
     
     
         2 . A bonded substrate, comprising:
 φ1 a first quartz-crystal substrate; and   φ1 a second quartz-crystal substrate bonded over the first quartz-crystal substrate, wherein   Euler angles (φ1, θ1, ψ1) of the first quartz-crystal substrate satisfy 83°≤φ1≤97°, 80°≤θ1≤100°, and 30°≤ψ1≤59°,   Euler angles (φ2, θ2, ψ2) of the second quartz-crystal substrate satisfy 88°≤φ2≤92°, 88°≤θ2≤92°, and 53°≤ψ2≤63°, and   a thickness of the second quartz-crystal substrate is 0.33 to 0.46 times a wavelength of a longitudinal leaky surface acoustic wave which propagates across a surface of the second quartz-crystal substrate.   
     
     
         3 . A bonded substrate, comprising:
 φ 1  a first quartz-crystal substrate; and   φ 1  a second quartz-crystal substrate bonded over the first quartz-crystal substrate, wherein   Euler angles (φ1, θ1, ψ1) of the first quartz-crystal substrate satisfy 74°≤φ1≤107°, 64°≤θ1≤116°, and 14°≤ψ1≤87°,   Euler angles (φ2, θ2, ψ2) of the second quartz-crystal substrate satisfy 89°≤φ2≤91°, 87°≤θ2≤93°, and 0°≤ψ2≤13° or 172°≤ψ2≤180°, and   a thickness of the second quartz-crystal substrate is 0.94 to 1.04 times a wavelength of a longitudinal leaky surface acoustic wave which propagates across a surface of the second quartz-crystal substrate.   
     
     
         4 . The bonded substrate according to  claim 1 , wherein propagation attenuation per unit wavelength of the longitudinal leaky surface acoustic wave is 0.01 dB or less. 
     
     
         5 . The bonded substrate according to  claim 1 , wherein the first quartz-crystal substrate and the second quartz-crystal substrate are bonded so as to come into direct contact with each other. 
     
     
         6 . The bonded substrate according to  claim 2 , wherein propagation attenuation per unit wavelength of the longitudinal leaky surface acoustic wave is 0.01 dB or less. 
     
     
         7 . The bonded substrate according to  claim 2 , wherein the first quartz-crystal substrate and the second quartz-crystal substrate are bonded so as to come into direct contact with each other. 
     
     
         8 . The bonded substrate according to  claim 3 , wherein propagation attenuation per unit wavelength of the longitudinal leaky surface acoustic wave is 0.01 dB or less. 
     
     
         9 . The bonded substrate according to  claim 3 , wherein the first quartz-crystal substrate and the second quartz-crystal substrate are bonded so as to come into direct contact with each other.